<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>定位</title>
		<style>
		 *{margin: 20px;}
		 div{
			 height: 100px;
			 width: 500px;
			 background-color: brown;
			 color: white;
		 }
		 #d2{
			 position: relative;
			 left: 100px;
			 top:50px;
			 background-color: #007AFF;
			 z-index: 199;
		 }
		 #d3{
			 z-index: 1000;
			 position: relative;
		 }
		</style>
	</head>
	<body>
		<div>1</div>
		<div id="d2">2</div>
		<div id="d3">3</div>
	</body>
</html>
